From: Pasha Tatashin <pasha.tatashin@oracle.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org,
linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
x86@kernel.org, kasan-dev@googlegroups.com,
borntraeger@de.ibm.com, heiko.carstens@de.ibm.com,
davem@davemloft.net, willy@infradead.org,
ard.biesheuvel@linaro.org, mark.rutland@arm.com,
will.deacon@arm.com, catalin.marinas@arm.com, sam@ravnborg.org,
mgorman@techsingularity.net, steven.sistare@oracle.com,
daniel.m.jordan@oracle.com, bob.picco@oracle.com
Subject: Re: [PATCH v9 08/12] mm: zero reserved and unavailable struct pages
Date: Wed, 4 Oct 2017 09:28:55 -0400 [thread overview]
Message-ID: <d743668c-6b7e-1775-a5b8-d6e997537990@oracle.com> (raw)
In-Reply-To: <20171004125743.fm6mf2artbga76et@dhcp22.suse.cz>
> I am not really familiar with the trim_low_memory_range code path. I am
> not even sure we have to care about it because nobody should be walking
> pfns outside of any zone.
According to commit comments first 4K belongs to BIOS, so I think the
memory exists but BIOS may or may not report it to Linux. So, reserve it
to make sure we never touch it.
I am worried that this patch adds a code which
> is not really used and it will just stay that way for ever because
> nobody will dare to change it as it is too obscure and not explained
> very well.
I could explain mine code better. Perhaps add more comments, and explain
when it can be removed?
trim_low_memory_range is a good example of this. Why do we
> even reserve this range from the memory block allocator? The memory
> shouldn't be backed by any real memory and thus not in the allocator in
> the first place, no?
>
Since it is not enforced in memblock that everything in reserved list
must be part of memory list, we can have it, and we need to make sure
kernel does not panic. Otherwise, it is very hard to detect such bugs.
next prev parent reply other threads:[~2017-10-04 13:30 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-20 20:17 [PATCH v9 00/12] complete deferred page initialization Pavel Tatashin
2017-09-20 20:17 ` [PATCH v9 01/12] x86/mm: setting fields in deferred pages Pavel Tatashin
2017-10-03 12:26 ` Michal Hocko
2017-10-03 15:07 ` Pasha Tatashin
2017-09-20 20:17 ` [PATCH v9 02/12] sparc64/mm: " Pavel Tatashin
2017-10-03 12:28 ` Michal Hocko
2017-10-03 15:10 ` Pasha Tatashin
2017-09-20 20:17 ` [PATCH v9 03/12] mm: deferred_init_memmap improvements Pavel Tatashin
2017-10-03 12:57 ` Michal Hocko
2017-10-03 15:15 ` Pasha Tatashin
2017-10-03 16:01 ` Pasha Tatashin
2017-10-04 8:48 ` Michal Hocko
2017-09-20 20:17 ` [PATCH v9 04/12] sparc64: simplify vmemmap_populate Pavel Tatashin
2017-10-03 12:59 ` Michal Hocko
2017-10-03 15:20 ` Pasha Tatashin
2017-09-20 20:17 ` [PATCH v9 05/12] mm: defining memblock_virt_alloc_try_nid_raw Pavel Tatashin
2017-09-20 20:17 ` [PATCH v9 06/12] mm: zero struct pages during initialization Pavel Tatashin
2017-10-03 13:08 ` Michal Hocko
2017-10-03 15:22 ` Pasha Tatashin
2017-10-04 8:45 ` Michal Hocko
2017-10-04 12:26 ` Pasha Tatashin
2017-09-20 20:17 ` [PATCH v9 07/12] sparc64: optimized struct page zeroing Pavel Tatashin
2017-09-20 20:17 ` [PATCH v9 08/12] mm: zero reserved and unavailable struct pages Pavel Tatashin
2017-10-03 13:18 ` Michal Hocko
2017-10-03 15:29 ` Pasha Tatashin
2017-10-04 8:56 ` Michal Hocko
2017-10-04 12:40 ` Pasha Tatashin
2017-10-04 12:57 ` Michal Hocko
2017-10-04 13:28 ` Pasha Tatashin [this message]
2017-10-04 14:04 ` Michal Hocko
2017-10-04 15:08 ` Pasha Tatashin
2017-09-20 20:17 ` [PATCH v9 09/12] mm/kasan: kasan specific map populate function Pavel Tatashin
2017-10-03 14:48 ` Mark Rutland
2017-10-03 15:04 ` Pasha Tatashin
2017-10-09 17:13 ` Will Deacon
2017-10-09 17:51 ` Pavel Tatashin
2017-10-09 18:14 ` Michal Hocko
2017-10-09 18:48 ` Will Deacon
2017-10-09 18:22 ` Will Deacon
2017-10-09 18:42 ` Pavel Tatashin
2017-10-09 18:48 ` Will Deacon
2017-10-09 18:59 ` Pavel Tatashin
2017-10-09 19:02 ` Will Deacon
2017-10-09 19:07 ` Pavel Tatashin
2017-10-09 19:57 ` Pavel Tatashin
2017-09-20 20:17 ` [PATCH v9 10/12] x86/kasan: use kasan_map_populate() Pavel Tatashin
2017-09-20 20:17 ` [PATCH v9 11/12] arm64/kasan: " Pavel Tatashin
2017-09-20 20:17 ` [PATCH v9 12/12] mm: stop zeroing memory during allocation in vmemmap Pavel Tatashin
2017-10-03 13:19 ` Michal Hocko
2017-10-03 15:34 ` Pasha Tatashin
2017-10-03 20:26 ` Pasha Tatashin
2017-10-04 8:45 ` Michal Hocko
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